1. Field of the Invention
The present invention generally relates to an electrophotographic image forming apparatus such as, for example, a copying machine, a printer or the like and, more particularly, to a monocomponent developing device for use in the electrophotographic image forming apparatus.
2. Description of the Prior Art
As a technique for developing an electrostatic latent image into a visible powder image in the electrophotographic image forming apparatus such as, for example, a copying machine, a printer or the like, two systems are well known in the art. One of them is a one-component or monocomponent system wherein only toner is employed as a developing material and the other of them is a two-component system wherein a developer mix containing toner and carrier beads are employed as a developing material.
The monocomponent developing system has recently come to be highly reevaluated because it makes use of a developing device which is simple in structure, compact in size and, hence, inexpensive to manufacture. The prior art monocomponent developing device is known which comprises a regulating member supported in contact with a surface of a toner carrier onto which toner is supplied. Not only can the toner supplied onto the surface of the toner carrier be triboelectrically charged by the regulating member, but the regulating member can also serve to regulate the amount of the triboelectrically charged toner attracted to the surface of the toner carrier. The regulated amount of the triboelectrically charged toner on the surface of the toner carrier is subsequently supplied onto an electrostatic latent image carrier such as, for example, a photoreceptor.
It has, however, been found that, with the prior art monocomponent developing device of the above discussed structure, a relatively large amount of toner tends to be attracted to an electrostatic latent image formed on a surface of the photoreceptor, while undesirably scattering externally around an electrostatic latent image on the surface of the photoreceptor at an initial stage of use of the developing device. In the worst case it may happen, abnormal fogging of images reproduced on a copying paper is often observed.